There's a quote I kinda forgot, but it goes something like:
"Did you experience the same thing 10 times, or did you experience 10 years worth?"
And I think this is true for a lot of real world experience, you don't necessarily have 10 year of it even though you've worked 10 years, you have 10 times the same experience.
OTOH, there's not a lot of places where a PoliSci Ph.D. would substitute for industry experience (or, for that matter, vice versa.) If you want to substitute an academic degree in that general space for “industry” experience, you go for public policy and/or public administration (or, arguably, law), not political science.
A PhD in government pretty much guarantees that you'll be retiring after a thirty year career as a GS-15 or SES. A 150k salary plus benefits may not be high for some STEM fields, but it's definitely not something to look down on.